Reactions of Cyclohexane on Platinum, Palladium, or Iridium-loaded H-ZSM-5 Zeolite Hydrohalogenated Catalysts

The catalytic hydroconversion of cyclohexane using catalysts containing H-ZSM-5 zeolite loaded with 0.35 wt% platinum, palladium, or iridium was studied in a pulse-type microreactor/GC system at atmospheric pressure. These catalysts were also either doped with 3.0% of HCl or HE The activities of these catalysts and the distribution of the products formed were found to depend on the dispersion of the metallic component as well as on the acidity, acid sites number, and strength in the catalysts. TPD of ammonia and hydrogen chemisorption were applied to evaluate acid site strength distribution and metals dispersion, respectively, in the catalysts. In case of the Pt- and Pd-containing catalysts, hydrochlorination enhanced the isomerization and dehydrogenation activities and selectivities of cyclohexane, but decreased its hydrocracking activity. However, catalyst hydrofluorination resulted in the reverse effects. Nevertheless, for the Ir-loaded catalyst, both hydrohalogenation treatments decreased the isomerization and dehydrogenation of cyclohexane. The Ir/H-ZSM-5 catalyst exhibited higher hydrogenolysis activities than did those acquired by the Pt- and Pd-containing catalysts.